As a wireless communication method is applied to diverse services, a location recognition service for detecting a location of a wireless device in addition to a data communication service is increasingly required. In order to satisfy the requirement for the location recognition service, diverse location recognition technologies and systems are suggested. The diverse location recognition technologies and systems will be described according to a transmitted/received signal creating method or a signal source applying method as follows.
When the location recognition technologies are divided according to the transmitted/received signal creating method, there are location recognition technologies using an infrared signal, a Radio Frequency (RF) signal, an ultrasonic signal, and an Ultra Wide Band (UWB) signal. Distance measuring precision of the location recognition technologies are differed according to each signal characteristic. For example, a distance error of several meters occurs in the location recognition technology using only the strength of the RF signal. On the other hand, the location recognition technology using the ultrasonic signal is precise to several centimeters.
As another dividing method, when the location recognition technologies are divided according to whether the same signal source is used in a data communication and ranging measurement procedure, the location recognition technologies are divided into location recognition technology differently using a transmitter/receiver for data communication and a transmitter/receiver for distance measurement, and location recognition technology performing data communication and distance measurement. As an example of the former technology where data communication is divided from distance measurement, a “Cricket” system uses an RF transmitter/receiver for data communication and uses an ultrasonic transmitter/receiver for distance measurement in parallel. On the other hand, as an example of the latter technology, a UWB system using one signal source can perform data communication and distance measurement using one transmitter/receiver.
Meanwhile, a Media Access Control (MAC) layer in a Wireless Personal Area Network (WPAN) used in data communication performs a function of forming a Personal Area Network (PAN) including a coordinator node and neighboring nodes. The MAC layer transmits data between the coordinator node and the neighboring nodes in the PAN.
In the communication technology on the MAC layer, diverse frames information, a channel scan method, a method for registering diverse channel scan devices, a channel access method, and a direct and indirect data transmitting method are defined. In the WPAN technology, functions of a physical layer and an MAC layer for simultaneously performing data communication and distance measurement are suggested.
Meanwhile, a distance between a specific node and reference nodes in a conventional WPAN can be measured based on information such as an angle difference and a time difference. The conventional ranging measurement technology using the time difference may adopt a two-way ranging (TWR) method for measuring a round trip time of data frame transmission between two devices without synchronizing a time through a cable as a technology of grasping a distance by measuring a transmission time of data or a packet.
A 2 dimensional (2D) coordinates value of the mobile node is acquired based on ranging measurement information among more than 3 reference nodes and mobile nodes on the basis of the physical layer and the MAC layer in the ranging measurement technology using the time difference. The ranging measurement information is transmitted to a positioning system capable of operating algorithm such as triangulation. The positioning system operates a final location coordinates value of the mobile node based on the transmitted ranging measurement information.
In the WPAN network layer, a mobile node location measuring procedure using a physical layer and an MAC layer is defined. The network layer operates according to a WPAN reference within a piconet and transmits the ranging measurement information to the positioning system via a plurality of piconets through data routing. The technology of measuring the mobile node location according to the reference of the network layer has a problem in that it is more difficult to be realized than the transmission technology on the MAC layer.